Hiding the signup form on profile pages

Small edit to hide the signup form (when logged out) on public profile pages. 

Review and merge.

Before:
![Twipster-Before](https://f.cloud.github.com/assets/104119/269979/08cf63b4-8fb5-11e2-8145-55d9dd7de8af.PNG)

After
![Twipster-After](https://f.cloud.github.com/assets/104119/269980/0905a4a6-8fb5-11e2-9dc2-6d0100d01cf0.PNG)